Draft technical document guidelines for Canadian drinking water quality - Antimony: Overview

Organization: Health Canada

Date published: December 2022

On this page

• Purpose of consultation
• Proposed guidelines
• Executive summary
• Application of the guidelines

Purpose of consultation

This guideline technical document evaluated the available information on antimony with the intent of updating the guidelines for antimony in drinking water. The purpose of this consultation is to solicit comments on the proposed guidelines, on the approach used for its development, and on the potential impacts of implementing them.

The existing guideline technical document on antimony, developed in 1999, recommended a maximum acceptable concentration (MAC) of 0.006 mg/L (6 µg/L) based on histological changes observed in the rat in a study by Poon et al. (1998). It was risk managed to take into consideration limitations in treatment technology. This document proposes a MAC of 0.006 mg/L (6 µg/L) for antimony in drinking water, based on histological changes in the liver and changes in serum biochemistry in the rat in the same study by Poon et al. (1998). The updated proposed MAC is risk managed to take into consideration treatment challenges of lowering the MAC (especially for private wells and small systems) without significant increase in health protection. The document was reviewed by external experts and subsequently revised.

This document is available for a 74-day public consultation period. Please send comments (with rationale, where required) to Health Canada via email at water-eau@hc-sc.gc.ca.

If email is not feasible, comments may be sent by postal mail to this address:

Water and Air Quality Bureau
Health Canada
269 Laurier Ave West, A.L. 4903D
Ottawa ON K1A 0K9

All comments must be received before March 8, 2023. Comments received as part of this consultation will be shared with members of the Federal-Provincial-Territorial Committee on Drinking Water (CDW), along with the name and affiliation of their author. Authors who do not want their name and affiliation shared with CDW members should provide a statement to this effect along with their comments.

It should be noted that this guideline technical document may be revised following the evaluation of comments received, and a drinking water guideline will be established, if required. This document should be considered as a draft for comment only.

Proposed guidelines

A maximum acceptable concentration (MAC) of 0.006 mg/L (6 μg/L) is proposed for antimony in drinking water.

Executive summary

This guideline technical document was prepared in collaboration with the Federal-Provincial-Territorial Committee on Drinking Water.

Exposure

Antimony naturally occurs in the environment in the form of organic and inorganic compounds. Antimony enters the environment from natural sources and human activities, with coal combustion, mining and smelting being the most important sources of release from human activities.

Canadians can be exposed to antimony via food, drinking water, air and consumer products. Exposure to antimony through environmental media, food and water is considered as low. Antimony may enter drinking water from plumbing solders in drinking water distribution systems. Food (including breast milk for infants) and beverages and, to a lesser extent, drinking water are identified as the main contributors for exposure to the general population.

Canadian data indicate that antimony is not commonly found in drinking water. The detection frequency for antimony in drinking water is very low and reported levels are largely below detection limits.

Health effects

Oral exposure to antimony may induce adverse effects mainly on the gastrointestinal tract and the liver. Kidney, cardiovascular, metabolic and developmental adverse effects have also been reported in the literature. The health based value (HBV) of 0.003 mg/L (3 µg/L) was derived based on histopathological changes in the liver and changes in serum biochemistry observed in animal studies. These effects are indicative of impacts on the liver.

The overall weight of scientific evidence indicates that antimony and related compounds are not considered carcinogenic via the oral route of exposure.

Analytical and treatment considerations

The development of a drinking water guideline takes into consideration the ability to both measure the contaminant and remove it from drinking water supplies. Several analytical methods are available for measuring antimony in water concentrations well below the proposed MAC. Measurements should be for total antimony, which includes both the dissolved and particulate forms of antimony in a water sample.

At the municipal level, treatment technologies that are available to achieve antimony drinking water concentrations below the proposed MAC include coagulation, adsorption, membrane filtration and coagulation followed by ultrafiltration. The performance of these technologies depends on factors such as antimony species, pH, coagulant type, coagulant dose and type of adsorbent.

At the residential scale, there are no treatment units currently certified for the removal of antimony from drinking water, however, the technology that is expected to be effective is reverse osmosis. Distillation may also be effective. When using such treatment units, it is important to send samples of water entering and leaving the treatment unit to an accredited laboratory for analysis to ensure that adequate antimony removal is occurring. Routine operation and maintenance of treatment units, including replacement of the filter components, should be conducted according to manufacturer specifications. It is recommended that water utilities develop a distribution system management plan to minimize the accumulation and release of antimony and co-occurring contaminants in the system. This typically involves minimizing the antimony concentration entering the distribution system and implementing best practises to maintain stable chemical and biological water quality conditions throughout the system, as well as to minimize physical any hydraulic disturbances.

Application of the guidelines

Note: Specific guidance related to the implementation of drinking water guidelines should be obtained from the appropriate drinking water authority.

All water utilities should implement a risk management approach such as the source-to-tap or water safety plan approach to ensure water safety. These approaches require a system assessment to:

• characterize the source water
• describe the treatment barriers that prevent or reduce contamination
• identify the conditions that can result in contamination and
• implement control measures

Operational monitoring is then established and operational/management protocols are instituted (for example, standard operating procedures, corrective actions and incident responses). Compliance monitoring is determined and other protocols to validate the water safety plan are implemented (for example, record keeping, consumer satisfaction). Operator training is also required to ensure the effectiveness of the water safety plan at all times.

The proposed guidelines are protective against health effects from exposure to antimony in drinking water over a lifetime. Any exceedance of the proposed MAC should be investigated and followed by the appropriate corrective actions, if required. For exceedances in source water where there is no treatment in place, additional monitoring to confirm the exceedance should be conducted. If it is confirmed that antimony concentrations in the water source are above the proposed MAC, then an investigation to determine the most appropriate way to reduce exposure to antimony should be conducted. This may include use of an alternate water supply or installation of an antimony treatment system. Where treatment is already in place and an exceedance occurs, an investigation should be conducted to verify treatment and to determine whether adjustments are needed to lower the treated water concentration below the proposed MAC.

Discoloration (coloured water) episodes are likely to be accompanied by the release of accumulated contaminants, including antimony, because dissolved antimony can adsorb onto deposits in the distribution and plumbing systems. Therefore, discolored water events should not be considered only an aesthetic issue; they should trigger sampling for metals and possibly distribution system maintenance.